CapsuleThe migratory Dark-billed Cuckoo breeds in the Brazilian semi-arid Caatinga biome during the rainy season, where its diet predominantly comprises insects from the orders Lepidoptera and Orthoptera, reflecting intermediate trophic niche diversity.AimsTo analyse the stomach contents of Dark-billed Cuckoo specimens collected opportunistically after fatal collisions, identifying dietary components, trophic niche breadth and patterns related to prey selection and seasonal resource availability.MethodsStomach contents of 72 Dark-billed Cuckoo specimens collected from four areas in north-eastern Brazil were analysed. Prey items were identified and quantified to determine taxonomic composition, frequency of occurrence, percentage of occurrence, biomass contribution and trophic niche amplitude. Morphometric measurements of the birds were compared with prey size to assess potential relationships.ResultsA total of 434 prey items, distributed among nine higher taxa, were identified, with Lepidoptera and Orthoptera predominating. Orthopterans represented the majority of the biomass ingested, while lepidopteran larvae were consumed most frequently. The standardized trophic niche breadth (Ba = 0.582) indicated intermediate resource diversity. No systematic relationship was found between prey size and bird morphology. Dietary patterns were consistent across study areas and aligned with previous findings for the species' feeding habits.ConclusionThe seasonal presence of the Dark-billed Cuckoo in the Caatinga is closely linked to resource availability during the rainy season, emphasizing the influence of abiotic factors on its migration and foraging strategies. The findings highlight the species' reliance on energetically rewarding prey, such as Orthoptera and Lepidoptera, and provide insights into its ecological role within the Caatinga biome.